Commitment of neutrophilic differentiation and proliferation of HL-60 cells coincides with expression of transferrin receptor - Effect of granulocytecolony stimulating factor on differentiation and proliferation

To examine the regulatory mechanisms of proliferation and maturation in neu trophilic lineage cells, we have tried to sort dimethyl sulfoxide (Me2SO)-t reated HL-60 cells into transferrin receptor (Trf-R) positive (Trf-R+) and negative (Trf-R-) cells. Differentiated Trf-R- cells expressed more formyl- Met-Leu-Phe receptor (fMLP-receptor) and ability of O(2)radical anion genar ation, as markers of differentiation, than Trf-R+ cells, and Trf-R cell dif ferentiation was markedly accelerated by the incubation with granulocyte co lony stimulating factor (G-CSF), On the other hand, Trf-R+ cells had a tend ency to proliferate rather than differentiate, and proliferation was enhanc ed by G-CSF, These results indicate that Trf-R expression coincides with th e commitment to proliferate or differentiate of HL-60 cells, and G-CSF acce lerates these commitments. G-CSF-induced tyrosine phosphorylation of STAT 3 in Trf-R- cells much more than in Trf-R+ cells. Protein 70 S6 kinase expre ssion was higher in Trf-R+ cells than in Trf-R- cells. Furthermore, p70 S6 kinase was hyperphosphorylated by G-CSF in Trf-R+ cells, but not in Trf-R- cells. Rapamycin, an inhibitor of p70 S6 kinase activity, inhibited G-CSF-d ependent proliferation of Trf-R+ cells and increased fMLP-R expression on t hese cells. These results suggest that commitment to proliferation and diff erentiation in Me2SO-treated HL-60 cells is preprogrammed and correlated wi th Trf-R expression, and G-CSF potentiates the cellular commitment. STAT 3 may promote differentiation of Me2SO-treated HL-60 cells into neutrophils, while p70 S6 kinase may promote proliferation and negatively regulate neutr ophilic differentiation.